1. Field of the Invention
The present invention relates to a shock absorber, and more particularly to a shock absorber having a shock absorbing spring and a buffering spring, which is able to provide a perfect shock absorbing effect.
2. Description of the Prior Arts
Referring to FIG. 1, a conventional shock absorber for a bicycle (including scooter, motorcycle and the like) is shown to comprise a cylinder body 10, a piston rod 11 extending into the cylinder body 10, and a spring 13 associated operably with the cylinder body 10 and the piston rod 11. The piston rod 11 includes a flange 111 and a cushion 112 defined at an end, the cylinder body 10 includes an adjustable stopping member 101 defined at a corresponding end, the piston rod 11 is movably positioned there by virtue of a limiter 12. Furthermore, a spring 13 is biased between the flange 111 of the piston rod 11 and the stopping member 101 of the cylinder body 10, such that the spring 13 is able to absorb the relative stress between the piston rod 11 and the cylinder body 10, and a deformation effect of the spring 13 is eliminated by the relative displacement between the piston rod 11 and the cylinder body 10. The conventional shock absorber described above has been commonly used, however, it has some disadvantages in operation as follows:
First, the spring 13 of the conventional shock absorber is normally in high elasticity coefficient in order to achieve an effective cushioning effect (the shock absorbing system is too stiff), however, the high elasticity coefficient spring is difficult to be deformed and compressed in case that the piston rod 11 and the cylinder body 10 relatively move under a pressure, moreover, it even won""t be deformed in case of a minor pressure (no cushioning effect), resulting in a disadvantage of the shock absorbing effect.
Second, in order to keep the shock absorbing effect continuous operation, the manufacturers usually employ shock absorbing spring with high elasticity coefficient, however, the restoring force and recovering speed of the spring 13 are great, which will lead to self-percussion when the spring 13 reaches the elasticity ultimate (return to the initial position), also cause collisions between the spring 13 and the piston rod 11, cylinder body 10 accompanied by noise.
Third, it should be pointed that the manufacturers usually don""t have the shock absorber equipped with a buffering device in order to save cost, the collisions during the restoring course of the spring will not be buffered, thereby, it not only impairs the shock absorbing effect but also results in an uncomfortable riding.
Targeting at solving the above disadvantages, an effective hydraulic buffer was invented, however, the line piping, leak-proof element and liquid oil are very expensive, furthermore, the line piping should be thickened and no gas hole allowed (material cost is high), a plurality of sealing members should be employed, all these factors increased the production cost of the hydraulic buffer.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional shock absorber.
In accordance with one aspect of the present invention, there is provided a shock absorber comprising: a piston rod movably received in a cylinder body, a shock absorbing spring is mounted to the cylinder body and biased therebetween, a buffering spring is mounted to an end of the piston rod in the cylinder body and biased between the inner edge of the cylinder body and the end of the piston rod.
The primary objective of the present invention is to provide a shock absorber having an ability of easing off the longitudinal expansion movement and compression movement of the shock absorbing spring so as to provide a smooth cushioning effect.
Another objective of the present invention is to provide a low cost shock absorber having a smooth cushioning effect by taking advantage of the relative motion of the two low cost springs.
A further objective of the present invention is to provide a shock absorber with comfortable cushioning effect, in which, the buffering spring eases off the longitudinal expansion movement and compression movement of the shock absorbing spring, preventing overly longitudinal expansion and self-percussion during the restoring course of the absorb shocking spring.
A further objective of the present invention is to provide a shock absorber, which is sensible to a slight shock by virtue of the restoring power of the buffering spring effectively reducing the compressing elasticity coefficient of the shock absorbing spring.